Welding apparatus



' Aug. 10,1943.

` w. A. WEIGHTMAN WELDING APPARATUS Filed May 5, 1959 2 Sheets-Sheet 1 A TTORNE Y Aug. 10, 1943.

w. A. WEIGHTMAN WELDING APPARATUS Filed May 5,V 1959 2 Sheets-Sheet 2 INVENTOR hfzZZz'am .f/Wea' himaw A TTORNE Y welds were made and cause a.

Patented Aug. 10, 1943 WELDING.` APPARATUS William A. Weightman,

or to Edward G. Budd adelphia, Pa., a corpo 3 Claims.

This invention relates to electric welding ap. paratus and more particularly to high-speed multiple point welding systems and to an improved method of welding.

Various types of electric weldingl machines have been designed for weldingv work pieces together at a great number of points, for example, thirty or more. Usually, a plurality of welding electrodes are utilized, arranged in pairs, each pair adapted to form a weld, and these are electrically connected to the secondary side of a transformer adapted to supply suitable welding current. With machines of this character, the welds are formed one at a time by bringing the pairs of electrodes into engagement with the work, passing current therethrough, dwelling, and then separating the electrodes. of such machines is that they are 'not rapid enough because several seconds are required to move each electrode into and out of engagement with the work and allow sufficient time for welding and dweil. Another difiiculty is that the welding pressure applied in making each weld and the time allowed for dwell may vary when fast operation is effected, whereby the resulting welds vary in strength and the joint between the work pieces is not uniform. Also, the potential of the current may vary due to the faulty rapidly made connections. It will be obvious that one bad' weld may ruin the entire work. This might happen after a considerable number of great loss of time and materials.

The present invention aims to provide an irnproved high speed welding machine and a method of welding for overcoming the diiiiculties and disadvantages heretofore encountered.

An object of the present invention is to increase the speed of securing work pieces requiring a plurality of welds.

Another object is to form a plurality of welds Philadelphia, Pa., assign- Manufacturing Co., Philration of Pennsylvania Application May 5, 1939, serial No. 271,823

(Ci. 21a- 4) A difficulty I which are subjected to uniform welding pressure and as a result join the work pieces uniformly at all points along the seam.

Another object is to provide assurance of sufncient dwell under pressure at the point of weld and maintain the pressure after fusion occurs to forge the work pieces together.

Another object is toprovide improved control means for supplying welding current to a. plurality of electrodes in rapid succession while maintaining all the electrodes in engagement with work. y

To accomplish the enumerated objects, the invention provides a machine wherein pairs of welding electrodes engage the work simultaneously and remain engaged until a Welding current has been successively passed through each pair of electrodes. In this manner is is possible to avoid the usual delay necessary in first mechanically engaging the work by each pair of electrodes, thereafter, passing the welding current therethrough and then dwelling for a few seconds prior to separating the electrodes and prior to engaging the subsequent pairs.

The invention further provides a simple, economically operable device for successively supplying a uniform welding current for a relatively short period of time rst to one pair of electrodes and then to others until all the welds have been completed.

In the accompanying drawings:

Fig. 1 is a diagrammatic View of a machine for forming a plurality of welds, illustrating an embodiment of the invention;

Fig. 2 is a fragmentary view, partly in section, of a pair of welding electrodes together with devices for operating and controlling the same; and

Fig. 3 is an enlarged sectional view, illustrating a mechanisrnfor moving the electrodes into.

engagement with the work which is adapted to insure proper dwelling of the welds.

Referring more particularly to'the drawings there is shown a welding machine which generally comprises a frame having work supports 9 and brackets ID for supporting the pressure operated mechanisms il adapted to move upper welding electrodesv l2 and lower welding electrodes I4 relative to the work; a transformer l5 for supplying suitable welding current from the secondary side thereof, control devices including switches i6 for connecting the electrodes to the secondary side of the transformer, a distributor Il for closing and opening the switches in rapid succession, and timing means I8 synchronized withthe distributor for periodically connecting the primary side of the transformer to a source of electricity during the intervals that one of the switches i6 is closed; and means I9 for supplying fluid pressure for operating the electrode moving mechanisms Il and the distributor l1.

. As illustrated more particularly' in Fig. l, any suitable number of upper and lower welding electrodes may be provided, for example thirty or forty (four of which are shown hereinfor illustrative purposes), and these may be arranged on the frame of the of any contour. The electrodes are and a lower 'ilar in construction, therefore, a detailed descrip tion of one pair will. serve for all. Also, the upper and. lower electrode moving mechanisms are sim ilar in construction, except that the upper mechanisms are adapted to move downwardly toward the work whereas the lower mechanisms are ins verted and are adapted to move the electrodes upwardly. Y

in Fig., 3, one of the mechanisms ll for moving an upper electrode is illustrated in detail. This mechanism, in its preferred form, comprises an p upright cylinder iii havingv an aperture 2i at its upper end for receiving a pipe 22 adapted to sup ply a iiuid pressure medium, such as oil, and a collar or bushing 23 threaded. into the lower end of the cylinder and having a shoulder El. A

plunger or piston rod it is slidahly mounted in the cylinder and has its lower end E@ extending through the 'pushing 23 to serve as means for securing an electrode holder or yoke El, intermediate its ends, the plunger has a flange 2d provided with an upper shoulder 2s 'and a lower shoulder @il adapted to abut the shoulder 2li of the bushing and thereby limit downward movement of the plunger with respect to the cylinder.,

The upper end of the plunger has a flange 3i threaded or otherwise secured thereon above which a piston S2 is slidaloly mounted in the cylinder. The piston preferably has a depending sleeve te provided with a bore for receiving the upper flanges@ of the plunger and a collar te extends about the plunger and is threaded into the bore at thel lower end or the sleeve. The collar has a shoulder d@ for engaging the underside of the nance si to prevent separation oi they piston and plunger, and to move the plunger up wardly with the piston.

The piston is adapted to move the plunger downwardly through the intermediation of a spring se, capable of withstanding suitable tension, which is coiled about the upper portionof the plungen The lower end of the coil is seated on the shoulder it of the plunger ange 25, and

the upper end abuts the lower end of the piston sleeve 3d or the collar 35. In this mannerD when the piston moves the plunger and, the electrode carried thereon downward, the electrode is yieldably pressed into contact with the work.

The spring normally is subjected to tension and is pre-compressed by compressing it beu tween the plunger shoulder sii and piston sleeve 3d so that it at all times'tends to urge the plunger downwardly with respect to the piston. With this arrangement, when the plunger is moved down-n wardly' and the electrode has engaged the worlsF the piston and plunger move relatively and further` compress the spring. When, during welding,

the work fuses and under forging pressure dem creases in thickness at the point of weld practically instantaneously, the spring causes the plunger and the electrode thereon to quiclny fol llow the work independently of movement ci the piston and thereby insures and maintains the ap r plicatlon o f proper forging and dwell pressure on the 'work (Fig. 3). l

The yokes or holders 2l for the welding electrodes are suitably attached nto the protruding ends v26 ofthe plungers 25, but are insulated therefrom., Preferably, each holder has a sleeve @d wherein the shank t of an electrode may be removably secured in the usual manner and has accesso a terminal dl adapted to be electrically connected to the transformer l5, as about to be described. The terminal l of each lower electrode is elec- 5 tricaily yconnected to a bus bar or conductor 5@ of low resistance which is secured to the frame of the machine', but is insulated therefrom, and

the bus bar in turn is electricallyv connected to one pole oi the secondary side rof the transformer i5. 1o Each upper electrode is provided with a switch l@ which may be or the Sylphon type shown, a1- though any other suitable switches may be utilined. These switches comprise an upper stationary broad heavy current carrying contact lit secured to the frame, but insulated therefrom, and electrically connected to the terminal il of an bellows El secured at one end to the contact 56 2c and adapted to move the contact et into and out of engagement with the contact 55; and a support 5s having the other end of the bellows secured thereto and provided with a port t@ for supplying pressure to the interior of the bellows from a pressure supply pipe di. The support de, as illustrated herein, maybe a bus bar t2 or the like which is secured to the machine frame, but insulated therefrom, and is electrically connected to the other pole of the secondary side-of 3o the transformer. The bus bar d2 may be electrically connected to the movable switch contacts ed through the bellows in which case the bellows are constructed of a good conducting metal, but preferably each switch has a flexible jumper of low resistance electrically connecting the bus bar to the contact 55. The bellows normally hold the contacts out o engagement by their resilient tendency to collapse and engage the contacts by expansion due to iiuid pressure therein.

luy suitable device may be utilized for opening and closing the switches to electrically connect and disconnect respectively the pairs of electrodes, and. as illustrated herein, there may be provided` an improved control device for regulating the pressure supplied to the bellows. The control. device includes a distributor il., comprising a cylindrical casing te provided withl an inner longitudinally extending bore t@ which tapers downwardly and inwardly at lits lower end Sli, and a cap et closing the upper end of the nected toa duid pressure supply pipe lil. The outer wall of the casing has a series of circumferentially spaced radially extending ducts or bores il each having one of the pipes @l secured thereto and each duct has a pair of ports extending radially through the casing to the bore BS. As about to be described, one of the ports, for ex ample, the upper port 'lll may serve as a pressure supply port whilethe other or lower port lsmay serve as a pressure relief port. The casing further is provided with an exhaust port i6 connected by a pipe 'il to the return of the uid pressure supply and extending radially through the casing to an annular recess i9 in the bore spaced longitudinally downwardly of the pairs of the ports ll and l. l

Mounted in the lower end of the bore of the casing there is a conical rotor or valve plug @il held downwardly by aspring el intermediate the upper end of the rotor and the lunderside of the cap ed. The rotor illustrated herein is adapted to successively connect each of the pressure ports it to the source ci pressure while connecting the upper electrode; a complementary lower Contact A et adjacent the contact 55; a pressure operated' This may be accomplished by providing the rotor with a conduit 85 which is in communication with the upper or pressure supply end of the bore 65 and extends downwardly through the rotor and then radially outwardly so that it is adapted to be brought'successively into registry with the pressure ports 14 of the casing. In order to relieve pressure in the switch bellows, the rotor is provided with a groove or passage 85 at the 'exterior and spaced downwardly from the pressure conduit which is adapted to connect the relief ports 15 to the exhaust port 15 of the casing. This groove is substantially annular but is interrupted below the outlet of the pressure conduit 85 so'that al1 ports 15 are connected to the exhaust except the port paired with the port 14 receiving pressure.

In order to rotate the valve plug or rotor 50 the lower end 81 thereof extends through the bottom of the distributor casing 55 and mounted thereon is a gear 89 adapted to be driven by a drive gear 90 mounted on a shaft 9i which is rotated by a second gear 92 thereon meshing with a drive gear 94 on the armature shaft of a suitable motor 95.

Cooperating with the distributor there is provided a timing switch 95 which operates a timer 91 adapted to electrically connect the primary side of the transformer at desired intervals to a source of electrical energy.l The timing switch is operated by a cam 99 on the shaft 9| and is so arranged that it is effective to closel the electrical circuit every time after one of the switches I6 has been closed. The timer is further arranged to maintain the electrical circuit for a relatively short period, for example, a fraction of a second,

and to break the circuit prior to separation of the contacts 55 and 56. By moving the contacts together and apart While the current is shut off, arcing between the contacts is eliminated.

While any suitable means may be provided for supplying fluid pressure, the means illustrated herein may comprise a supply tank |00, a motor |l, and a rotary compressor pump |02 driven by the motor. A pipe |04 is connected to the suction or intake side of the pump and this pipe extends into the tank below the liquid level thereof to supply fluid to the pump. At the pressure or exhaust side of the pump, there is a pressure supply main |05 to which the distributor pressure supply pipe is connected. The supply main may be provided with a pressure regulator |05 adapted to maintain a uniform pressure and having a by pass pipe |01 connected to a return pipe |09 for returning excess nuid to the tank. The pressure main is adapted to supply pressure to the electrode operating cylinders through a three way valve H0. One outlet of the valve is connected to the main |05, another outlet is connected to a feeder pipe |I| having the electrode operating cylinder supply pipes 22 connected thereto in parallel, and the third outlet is connected to return pipe |09. The valve ||0 has a slidable piston ||2 which is so arranged that in one position pressure is supplied from the main 505 to the feeder pipe III, and in another position, the feeder pipe |I| is connected to the return pipe |09 to relieve pressure in the electrode operating cylinders.

In operation of the machine the work W is placed between the pairs of upper and lower electrodes and is positioned so that the electrodes will contact it at points where welds are to be formed. The piston H2 of the valve ||0 is then moved into a position permitting the dow of pressure from the pressure main |05 to the feeder pipe i I whereby pressure is simultaneously admitted to the cylinders 20. The pistons 32 then move the piston rods or plungers 25 toward the work and cause the electrodes to simultaneously engage the work. While this occurs the springs 39 intermediate the pistons and plungers are further compressed, preferably to an extent where they are completely collapsed or fully compressed.

The distributor motor is then started and as the valve plug or rotor revolves within the distributor casing, pressure is successively admitted to the switch bellows 51 preferably one at a time, through the rotor conduit 85, casing part 15, pipe 5| and part 60 in the bellows support. For example, as shown in Fig. 1, if bellows 51A is subjected to pressure, the contacts 55 and 55 of switch IBA are caused to engage to close the electrode circuit. Meanwhile, as will be observed, the bellows 51B, 51C, and 51D are not subjected to pressure and serve to hold apart the contacts 'of their respective switches IBB, IGC, and ISD.

Every time a switch has been closed by the diS- tributor the timing switch electrically connects the primary side of the transformer which causes welding current to flow through a pair of welding electrodes for a welding period of a fraction` of a second. As the weld is formed the work is fused at the point of weld and decreases slightly in thickness. As illustrated in Fig. 3, when this occurs, the fully compressed springs 39 in the cylinders cause the electrode operating plungers 25 to move quickly toward the work and force the electrodes against the work with suitable forging pressure. These springs exert a pressure as great as the pressure exerted upon the piston by the uid. This is particularly desirable where a iiuid pressure medium such as oil is utilized, because due to the sluggish characteristics and inelasticity of such iiuids, the fluid cannot be depended upon to move the pistons 32 rapidly and cause the electrodes to follow-up the work and continue to apply suiicient pressure on the work at the required instant of fusion. Pre-compression of the springs, as utilized herein, together with additional compression during engagement of the work, loads the springs and provides the necessary forging pressure, independently of movement of the pistons 32. Such a spring may be of advantage even where the fluid pressure is compressed air, for it eliminates the inertia of the piston 32 in the follow-up movement, the movement being restricted to the piston rod and electrodefabove.

After current has passed lthrough the electrodes, for example, electrodes |2B and MB, the groove connects the relief port,15 to the exhaust port 15' and the pressure in the bellows is relieved to cause the bellows to open the switch contacts 55B and 55B, prior to a succeeding operation of the timing switch. As the rotor continues to rotate, succeeding ports 14 admit pressure to their respective switch bellows and electric current is established by the timing switch at instances when the switches are closed. When. all electrodes have formed a weld the rotor is stopped and the source of electric current for the transformer is disconnected. No arcing will result at the switch contacts 55 and 55, since setting the timer switch properly. the now of welding current may be restricted from nowing except after the contacts 55 and 55 are closed, and the welding current cut oif by the timer prior to the opening of the contacts. If desired the assenso 19, 1937, now Patent No. 2,229,993, datedl January 28, 1941, thereby speeding up the ali= ment of the valve ports. Should the timer :fail to function in cutting od the ow oi welding our rent, such arc as would ordinarily occur 'at the `Work by the separation of the electrodes `will in the present system occur at the switch contacts 55 and 5t, thus avoiding any possible spoiling of a work piece from this cause.

The precompressed spring 39 will be ordinarily under a compression nearly equal to the welding pressure desired, so that little worls by the duid pressure medium will be required in engaging the electrodes and placing the spring underiurther compression, thus cutting down the necessary ilow of pressure medium.

After Welding current has been apped to the respective pairs of electrodes, for example, to the electrodes liB and MB (Fig. l) to form the weld, the electrode operating mechanism urges the electrodes against the work to apply deve ff pressure to the weld which continues during the formation of succeeding welds. After all' welds have been formed, this dwelling pressure is maintained for a few seconds to finish the last weld. Thereafter the piston M2 of the pressure control valve lic is moved into a, position to connect the feeder pipe lll to the return pipe lil, whereupon pressure exerted upon the electrode operating cylinder pistons 32 is relieved. The pistons $2 and the plungers 25 then move the electrodes away from the work to permit the work to be removed from the machine by gravity and spring Ml.

It will thus appear that there is provided an apparatus capable of enacting a large number of .welds in a period slightly in excess of that required to switch the current from one set o electrodes to the other in rapid succession. The usual delay necessitated in engaging and disengaging individual electrodes prior to engagement of succeeding electrodes is thus avoided, and the consequent time required greatly decreased.

.As various changes may be made in the form, construction and arrangement of parts without departing from the spirit and scope ci the invention and without sacricing its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a lting sense.

While the present application is outstandingly directed to the switching means for the welding current d to the arrangement of such means relatively to the electrodes and the source oi our rent supply, applicants copending application Serial No. aiLZQS, Welg gun, led Sep-l ternber i8, i941, which is a division oi the present application, isv directed to the particular means :for moving the electrodes and for exerting pressure therebya What Si claim is: V

l. The combination with a pair o welding electrodes, ci a uid pressure device ior moving at least one ci said electrodes, a stationary sup port adjacent said electrodes, a pair or conductors insulated from each other and carried by said support, connections from each conductor to an electrode at least one connection being adapted for relative movement between the respective electrode and conductor, a movable con tact for cooperation with one of said conductors to open and close the circuit through said elec trades, a Sylplion type duid pressure device for 'actuating said movable contact, and a exible connection bridging said Sylphon device.

2. lllde combination with a pair of welding electrodes ci a uid pressure device tor moving at least one of said electrodes, a stationary sup= port adjacent said electrodes, a pair of conductors insulated from each other and carried by said support, electrical connections from each conductor to an electrode, at least one connection being adapted for relative movement between the respective electrode and conductor, said one connection including a series switch having a xed contact and a movable contact, and an expansible meber adapted to iorce the movable contact into vyieidable engagement with vsaid iixed comE met.

3. The combination with a pair of welding electrodes of a duid pressure device for moving at least one of said electrodes, a stationary support adjacent said electrodes, a pair of conductors insulated from each other and carried by said support, electrical connections from each conductor -to an electrode, at least one connection ben-:f adapted for relative movement between the respective electrode and conductor, said one coection including a series switch having a d contact and a movable contact, i

and an e 'we rf le member adapted to'iorce the movable contact into yieldable engagement with said need contact, iixed and movable contacts and said capansible member Yf if between ald 601111116215016.

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